The present invention is an improvement on the Gifford-McMahon cycle. Familiarity with said cycle is assumed. Representative prior art patents teaching such cycle include U.S. Pat. Nos. 2,966,035; 3,188,818; 3,218,815; and 4,305,741.
In certain environments, such as a super conducting quantum interference device, the magnetic flux of an electric motor cannot be tolerated. Hence, there has been proposed a fluidic unit to cause movement of the displacer. For example, see U.S. Pat. No. 4,310,337. Fluidic refrigerators have certain disadvantages, namely lack of control of the displacers so that a full pressure charge of gas is introduced in each cycle and the objectional noise when the displacer bottoms out at the end of each stroke. The present invention solves those problems.